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对基于差分群时延的磁场测量方法中光纤布拉格光栅(FBG)结构的影响进行了分析。利用耦合模理论和传输矩阵法仿真,分析了均匀FBG的长度和折射率调制系数对传感系统测量范围和灵敏度的影响。同时改变FBG制作结构,研究了啁啾光栅、相移光栅和切趾光栅的差分群时延性能。并对各种光栅结构的差分群时延峰值大小进行了理论和实验比较。对均匀光栅和相移光栅的实验比较测量表明,采用相移光栅结构可以明显提高传感测量系统的灵敏度,实验数据和理论吻合较好。
The influence of fiber Bragg grating (FBG) structure in magnetic field measurement method based on differential group delay is analyzed. The effects of uniform FBG length and refractive index modulation coefficient on the measurement range and sensitivity of the sensing system were analyzed by using coupled-mode theory and transmission matrix method. At the same time, the fabrication structure of FBG was changed, and the performance of differential group delay of chirped grating, phase shift grating and apodized grating was studied. The theoretical and experimental comparisons of the differential group delay peak sizes of various grating structures are made. The experimental comparison of uniform grating and phase-shift grating shows that the sensitivity of the sensing system can be significantly improved by adopting the phase-shift grating structure. The experimental data are in good agreement with the theory.